1. Field of the Invention
The present invention relates generally to rotating unions and, more particularly, is concerned with an internally-located dual flow rotating union for transmitting pressurized fluid into and out of an end of a rotating shaft.
1. Description of the Prior Art
It is conventional practice to transmit a fluid from a stationary source into and out of a shaft of a machine, such as a turbine generator and motor, as the machine is operating with the shaft rotating The shaft may require the fluid for cooling or for some other purpose A connection or joint, generally referred to as a rotating union, is used in the prior art for introducing fluid from the stationary source into the rotating shaft and discharging the fluid therefrom. Many different versions of both external and internal (in-the-shaft mounted) rotating unions are commercially available, such as ones manufactured and marketed by Deublin Company of Northbrook, Illinois.
Dual flow rotating unions are ones which introduce and discharge fluid into and from the same end of the rotating shaft. Present designs of externally mounted dual flow rotating unions and of dual flow rotating unions employing ball bearings have several drawbacks. Externally mounted dual flow rotating unions are susceptible to shaft induced shock loads which can damage the bearings and seals of the rotating union. Externally mounted rotating unions also require considerable length beyond the end of the shaft, significantly increasing the overall length of the rotating assembly.
Ball bearings used in rotating unions have a limited life which is highly dependent on both the radial load and the axial preload. Special assembly procedures must be used to ensure proper preload. Also, the bearings must be replaced on a periodic basis to preclude unscheduled equipment shutdown due to bearing failure. Ball bearings, even those designed for quiet operation, are inherently "noisy". Further, ball bearings used in rotating assemblies must be protected from the operating fluid which can introduce foreign material into the bearings and can cause corrosion of the bearing races and balls; either of these can cause premature failure of the bearings. Special bearing seals and/or sealing and purging schemes are used to protect the ball bearings.
Consequently, a need exists for a dual flow rotating union design which will avoid the above-mentioned drawbacks.